U.S. patent number 7,061,839 [Application Number 09/917,700] was granted by the patent office on 2006-06-13 for optical information recording medium and recording/reproducing apparatus for such medium.
This patent grant is currently assigned to Victor Company of Japan, Ltd.. Invention is credited to Atsushi Hayami, Makoto Itonaga, Junichiro Tonami.
United States Patent |
7,061,839 |
Itonaga , et al. |
June 13, 2006 |
Optical information recording medium and recording/reproducing
apparatus for such medium
Abstract
An optical information recording medium (1) is composed of a pit
recording area (2), wherein various control information is recorded
by a prepit, and a user recording area (3) having a guide groove
formed in a groove format, and a phase depth for the prepit and the
groove are approximately the same wherein the phase depth is less
than or equal to .lamda./10, wherein .lamda. is a wavelength for
reproducing light source. A recording/reproducing apparatus (4) for
the optical information recording medium (1) includes decoding
means (12) for decoding information by detecting a tangential
push-pull reproduced signal from the prepit recording area (2) and
detecting an aggregated signal from the user recording area
(3).
Inventors: |
Itonaga; Makoto (Yokohama,
JP), Hayami; Atsushi (Yokohama, JP),
Tonami; Junichiro (Yokohama, JP) |
Assignee: |
Victor Company of Japan, Ltd.
(Yokohama, JP)
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Family
ID: |
18723637 |
Appl.
No.: |
09/917,700 |
Filed: |
July 31, 2001 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20020015367 A1 |
Feb 7, 2002 |
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Foreign Application Priority Data
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Jul 31, 2000 [JP] |
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2000-230711 |
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Current U.S.
Class: |
369/47.35;
369/124.12; 369/47.21; 369/59.22; G9B/7.025; G9B/7.029;
G9B/7.039 |
Current CPC
Class: |
G11B
7/0053 (20130101); G11B 7/007 (20130101); G11B
7/24085 (20130101); G11B 20/10009 (20130101) |
Current International
Class: |
G11B
7/00 (20060101) |
Field of
Search: |
;369/59.11,59.13,59.15,59.2,59.21,59.25,124.02,124.06,124.12,124.13,124.14,124.15 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Hayashi, H., et al., "DVD Player Using a Viterbi Decoding Circuit,"
IEEE Transactions on Consumer Electronics, vol. 44, No. 2, May
1998, pp. 268-272. cited by other .
Bouwhuis, G., et al., Principles of Optical Disc Systems, Chapter
2.2., "Scanning Spot Microscopy," pp. 8-23, Adam Hilger, Ltd.,
Bristol and Boston, 1985. cited by other.
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Primary Examiner: Korzuch; William
Assistant Examiner: Goma; Tawfik
Attorney, Agent or Firm: Connolly Bove Lodge & Hutz
LLP
Claims
What is claimed is:
1. A reproducing method for reproducing information from an optical
disc having a pit recording area recorded with various control
information by a prepit, and a user recording area having a guide
groove as a track, the method comprises the steps of: irradiating a
laser beam from a light source on the disc; receiving reflection
light from the disc by a light detector, wherein the light detector
having four areas defined as first area to fourth area in a first
direction of a tangential line of the track and in a second
direction orthogonal to the tangential line, and wherein a first
pair of a first area and a second area and a second pair of a third
area and a fourth area are both aligned in the first direction, a
third pair of the first area and the fourth area and a fourth pair
of the second area and the third area are both aligned in the
second direction; detecting a pit signal as a control information
signal in a form of a tangential push-pull reproduced signal by
using the third pair and fourth pair, when the laser beam is
irradiated on the pit recording area, wherein the tangential
push-pull reproduced signal is the difference of pit signals
detected by the third pair and fourth pair; detecting a user
information signal as an aggregated signal by using every first to
fourth area, when the laser beam is irradiated on the user
recording area, wherein the aggregated signal is the aggregation of
signals detected by every first to fourth area; and decoding the
tangential push-pull reproduced signal or the aggregated
signal.
2. A reproducing method as claimed in claim 1, wherein said
decoding step obtains a signal equalized in a desirable partial
response characteristic from the tangential push-pull reproduced
signal by using a waveform equalizing circuit.
3. A reproducing method as claimed in claim 1, wherein said
decoding step decodes the tangential push-pull reproduced signal
and the aggregated signal by using a viterbi decoder.
4. A reproducing method as claimed in claim 2, wherein a partial
response polynomial equation for equalizing the tangential
push-pull reproduced signal in the partial response characteristic
is 1+D-D.sup.2-D.sup.3.
5. A reproducing method as claimed in claim 2, wherein said
decoding step decodes the tangential push-pull reproduced signal
and the aggregated signal by using a viterbi decoder.
6. A reproducing method as claimed in claim 3, wherein a partial
response polynomial equation for equalizing the tangential
push-pull reproduced signal in the partial response characteristic
is 1+D-D.sup.2-D.sup.3.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical information recording
medium such as an optical disc or an optical card, and to a
recording/reproducing apparatus for such the recording medium.
2. Description of the Related Art
Generally, a disc area of a recordable optical disc is divided into
a user recording area and a pit recording area recorded with
various control information. The various control information is
such information as an address information related to the user
recording area, an information for a most suitable recording power
and a recording waveform, a provenance information (such as a
manufacturing information), or a copy administrative information,
or a copy protection information etc.
The information of which to be recorded and the recording method
for such information depend on a format of the user recording area.
The user recording area contains a groove for tracking. There are
provided format types of a groove format for a recording
information only on the groove and a land-groove format for the
recording information on both land and groove.
As focusing on a physical figuration of the groove, there are two
differences in the groove format and land-groove format. First, the
groove format has a physically narrower track pitch than the
land-groove format. The track pitch for land-groove format in view
of information is a width of the land or groove, and the physical
track pitch for the land-groove format will be a sum of both
widths. On the other hand, the groove format has a physical track
pitch equivalent to the track pitch in view of information, and the
groove width for the recording information is equivalent to a half
width of the track pitch. Accordingly, the track pitch for groove
format is equivalent to approximately a half width of the track
pitch of land-groove format.
Second, the groove format has a shallower phase depth than the
land-groove format. The land-groove format utilizes a groove having
a phase depth of approximately .lamda./6 to suppress cross-talk
from the land to groove or the groove to land at the reproducing
condition. The ".lamda." represents a wavelength of reproducing
light source. On the other hand, the groove format utilizes a
shallower phase depth because it has a thinner groove width that
the reproducing output of recorded information is low. Typically,
the phase depth is less than .lamda./8. The phase depth depends on
a disc system, for example, a magneto-optical disc utilizes a
.lamda./8 phase depth. Further, disc types of a phase change
optical disc, such as CD-RW and DVD-RW discs, utilize a phase depth
of less than .lamda./10, desirably less than .lamda./15. The reason
why the phase depth of groove is shallower in the latter is that to
maintain compatibility with a ROM type disc in a signal to be used.
Further, a system for a next generation such as the system using a
semi-conductor laser of 400 nm wavelength utilizes shallower groove
of less than .lamda./10, desirably .lamda./13 to .lamda./20 to
obtain higher level of reproducing signal.
The following is the reason why that the groove format is superior
to the land-groove format. The land-groove format has a problem of
having a different amount of offset for a land or a groove at the
optimum operating point in a focus or a tracking servo system under
recording/reproducing operation. On the other hand, as to the
groove format, the information is recorded on to a groove of single
stroke line from inner to outer circumference so that the disc
format can be simple and the recording/reproducing operation for
the disc can be simple. Further, a disc of the ROM type also has a
groove of single stroke line so that the compatibility of format
between a ROM type disc and a recordable disc can be
maintained.
The groove format does not have a problem of having a different
offset amount in optimum operating point of the focus and tracking
servo system. Accordingly, the groove format is considered to be
advantageous for the next generation format. A
recording/reproducing method for the groove format has been
disclosed in the Japanese Patent Laid-open Publication No.
10-222874 that the information is recorded on or reproduced from an
optical information recorded medium having an information area of a
Lin (Lead-in) area where the PCA, PMA, an address information and a
control information necessary for recording and reproducing
superimposed on a wobbling pregroove as a preformat information, a
program area where the user information constitutes a pregroove and
a Lout (Lead-out) area, from an inner to outer circumferences, by
being synchronized with preformat information and controlling
revolution of the disc and a pulse for recording data. The
pregroove is wobbled based on the standard signal having a
predetermined frequency combined with an address information and a
control information.
However, if the control information has been recorded wobblingly,
it is difficult to wobble the groove in high speed and
consequently, an amount of information which can be recorded
decreases. To solve this problem, information is recorded by
utilizing a pit format like the land-groove format.
The pit and groove should be formed in a same depth because the pit
and groove is recorded on a photo-register applied to an original
glass disc with an original disc recording apparatus. Based on the
original disc recorded as mentioned above, a plastic disc will be
manufactured. A plastic molding and transcription or the like for
the pit and groove slightly differs from each other but the phase
depth of the pit and groove will be technically the same. A disc
manufactured as mentioned above having the same phase depth of the
pit and groove with less than .lamda./10 nm can provide with only a
very small amount of reproducing signals. Such a reproducing signal
has a small level with less S/N ratio, which is not sufficient for
decoding. In addition, making different phase depth for each pit
and groove will cause a manufacturing process for optical
information recording disc complicated and decrease a manufacturing
productivity.
SUMMARY OF THE INVENTION
Accordingly, in consideration of the above-mentioned problems of
the related art, an object of the present invention is to provide
an optical information recording medium (1) including a pit
recording area (2) recorded with various control information by a
prepit and a user recording area (3) having a guide groove, wherein
a track is formed by groove format and a phase depth for the prepit
and the guide groove are approximately less than or equal to
.lamda./10, where .lamda. is the wavelength of a light source (5)
for reproducing information from the optical information recording
medium (1).
Another object and further aspect of the present invention is to
provide a recording and reproducing apparatus (4) for an optical
information recording medium (1) including a pit recording area
recorded with various control information by a prepit, and a user
recording area (3) having a guide groove, wherein a track for the
user recording area is formed in groove format, the recording and
reproducing apparatus including decoding means (12) for decoding
information from the optical information recording medium (1) by
detecting a signal in a form of a tangential push-pull reproduced
signal from the pit recording area (2), and detecting another
signal in a form of an aggregated signal from the user recording
area (3).
Another object and further aspect of the present invention is to
provide a recording and reproducing apparatus (4) in which the
decoding means (12) includes a waveform equalizing circuit (13) for
obtaining a desirable partial response characteristic from the
tangential push-pull reproduced signal.
Another object and further aspect of the present invention is to
provide a recording and reproducing apparatus (4) in which the
decoding means (12) is a viterbi decoder.
Another object and further aspect of the present invention is to
provide a recording and reproducing apparatus (4) in which a
partial response polynomial equation for equalizing reproduced
signal in the partial response characteristic is
1+D-D.sup.2-D.sup.3.
Other objects and further features of the present invention will be
apparent from the following detailed description when read in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a plan view of an optical information recording medium
according to a first embodiment of the present invention.
FIG. 2 is a partially enlarged plan view of a border portion of a
user recording area and a pit recording area of the optical
information recording medium shown in FIG. 1 according to the
present invention.
FIG. 3 is a block diagram for explaining a recording and
reproducing apparatus for an optical information recording medium
according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a reproduced signal output in relation
to a phase depth of a pit.
FIG. 5 is a diagram showing a signal output in relation to a
standardized spatial frequency.
FIG. 6(a) is a diagram showing a reproduced signal from a DVD disc
by a PP detecting method.
FIG. 6(b) is a diagram showing a reproduced signal from a DVD disc
by an aggregated signal method.
FIG. 7 is a diagram showing a power spectrum of reproduced signal
by the PP detecting method and the aggregated signal method.
FIG. 8 is a block diagram showing a decoding circuit for decoding a
tangential push-pull reproduced signal.
FIG. 9 is a diagram showing a power spectrum of a PR(1, 1, 0, -1,
-1) characteristic signal.
FIG. 10 is a diagram showing an eye-pattern by plotting a sample
point of waveform having the power spectrum shown in FIG. 9.
FIG. 11 is a diagram for explaining an intergradation of viterbi
decoder suitable for the PR(1, 1, 0, -1, -1).
FIG. 12 is a diagram showing a power spectrum for a signal having a
characteristic of the PR(1, 1, 0, -1, -1).
FIG. 13(a) is a diagram for explaining an intergradation of viterbi
decoder for a PP reproduced signal in the PR(1, 1, 0, -1, -1).
FIG. 13(b) is a diagram for explaining an intergradation of viterbi
decoder for an aggregated reproduced signal in the PR(1, 1, 0, -1,
-1).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
FIG. 1 is a plan view of an optical information recording medium
and FIG. 2 is a partially enlarged plan view of a border portion of
a user recording area and a pit recording area of the optical
information recording medium shown in FIG. 1.
As shown in FIG. 1, an optical information recording medium 1, such
as an optical disc, is formed with a pit recording area 2 wherein
various control information is recorded by a prepit adjacent to the
disc center, a user recording area 3 having a guide groove,
adjacent to the pit recording area 2. The user recording area 3 is
formed by a groove format. Respective phase depth of a prepit and a
groove in the user recording area 3 is approximately the same and
the depth is less than .lamda./10 wherein the .lamda. is a
wavelength of a light source for reproducing signal.
The reason why the phase depth is less than .lamda./10 is because a
larger level of reproduced signal can be obtained. It is desirable
to have phase depth for prepit and groove less than .lamda./13 to
obtain a reproduced signal at practical use. Further, it is
necessary to have phase depth less than .lamda./20 to obtain a
tracking error signal in good condition. Accordingly, the phase
depth for prepit and groove are preferred to be in a range of
.lamda./13 to .lamda./20 to obtain both reproduced signal and
tracking error signal in good condition.
A control information includes information for
reproducing/recording control such as a construction for disc
format and address, disc ID (identification) copy administration
information such as a name of manufacturer or copy protection,
information for preventing copy and protecting contents, an optimum
recording power, a strategy for an optimum recording, and control
information for recording or reproducing at an optimum power.
Some portion of the control information may be recorded in the pit
recording area 2 by the same way of recording method for the user
recording area 3.
As the control information is recorded in the pit recording area 2
by prepit and the user recording area 3 consists of a guide groove
so that a large capacity of information can be recorded in the user
recording area 3. The pit recording area 2 can be formed in the
area other than the area contiguous to the center of the optical
information recording medium 1.
FIG. 3 is a block diagram for explaining recording/reproducing
apparatus for an optical information recording medium according to
the present invention. A recording/reproducing apparatus 4 is
composed of a light source 5 such as semi-conductor laser, a
collimator lens 6 for condensing light outputted from the light
source 5, a polarizing beam splitter 7 for polarize and separate a
light passed through the collimator lens 6, a prism 8 for
reflecting light separated by the polarizing beam splitter 7, an
object lens 9 for condensing light reflected by the prism 8 onto an
optical information recording medium 1, a plurality of cylindrical
lens 10 for providing astigmatism of reflection light from the
optical information recording medium 1 through the object lens 9,
the prism 8 and the polarizing beam splitter 7, and a light
detector 11 for receiving reflection light from the optical
information recording medium 1 through the cylindrical lens 10.
The light detector 11 has four areas defined as A, B, C and D in
the direction of a tangential line of the track and in the
tangential direction orthogonal to the tangential line. A user
information reproduced from the user recording area 3 is detected
as an aggregated signal of signals a, b, c and d (a+b+c+d) which
are outputted from each of the above four areas A, B, C and D. This
is called an aggregated detecting method.
A tracking error signal is detected by the difference of signals
divided in the direction of tangential line of the track, i.e.
(a+b)-(c+d). Simultaneously, an address information recorded by
wobbling is also detected by this error signal.
A focus error signal is detected by the difference of signals from
the opposing corner, i.e. (a+c)-(b+d) A pit signal reproduced from
the pit recording area 2 is detected by the difference of two areas
divided in the tangential direction orthogonal to the track, i.e.
(a+d)-(b+c). This is called a tangential push-pull detecting method
(hereinafter referred to as "PP detecting method"). The signal
(a+d)-(b+c) is hereinafter referred to as tangential push-pull
reproduced signal.
The recording and reproducing apparatus 4 operates, in a
reproducing mode, a light outputted from the light source 5 is
exposed on the optical information recording medium 1 through the
collimator lens 6, the polarizing beam splitter 7, the prism 8 and
object lens 9, and a refection light from the recording medium 1 is
reflected through the object lens 9, the prism 8, the beam splitter
7 and the cylindrical lens 10 and received by the light detector
11, and then the user information, tracking error information,
focus error information and pit information are obtained by
calculation of signals outputted from the four areas A, B, C and
D.
In a recording mode, a light outputted from the light source 5 is
exposed on the recording medium 1 through the collimator lens 6,
the polarizing beam splitter 7, the prism 8 and object lens 9 to
record information on the recording medium 1.
The output of reproduced signal has been detected by using the
aggregated detecting method and the PP detecting method
corresponding to phase depth of the pit and standardized spatial
frequency. The shape of the pit is rectangular. The standardized
spatial frequency is defined by the number of aperture NA,
wavelength .lamda. and linear velocity of the recording medium
1.
FIG. 4 is a diagram showing a reproduced signal output in relation
to phase depth of a pit. The horizontal axis is a phase depth of
pit (.lamda.), and the vertical axis is an output level of
reproduced signal. The solid line shown in FIG. 4 is the result of
using the PP detecting method and the dotted line shown in FIG. 4
is the result of using the aggregated detecting method.
As shown in FIG. 4, the output of reproduced signal for the
aggregated detecting method increases as the phase depth becomes
deeper and it becomes maximum at .lamda./4, and then decreases. On
the other hand, the output of reproduced signal for the PP
detecting method increases as the phase depth becomes deeper and it
becomes maximum at .lamda./8, and then it decreases. The output of
reproduced signal for the PP detecting method is higher than the
output of reproduced signal for the aggregated method less than or
equal to 0.175.lamda.. This indicates that the PP detecting method
can obtain higher output signal level than the aggregated detecting
method if the phase depth of pit is less than or equal to
.lamda./10. In addition, a reproduced signal in good condition, and
a tracking error signal in good condition can be obtained when the
phase depth of pit is within the range of .lamda./13 to
.lamda./20.
FIG. 5 is a diagram showing a signal output in relation to a
standardized spatial frequency. The horizontal axis is a
standardized spatial frequency, and the vertical axis is an output
level of reproduced signal. The solid line shown in FIG. 5 is the
result of using the PP detecting method and the dotted line shown
in FIG. 5 is the result of using the aggregated detecting
method.
In FIG. 5, the output of reproduced signal for the aggregated
detecting method decreases as the standardized spatial frequency
increases. On the other hand, the output of reproduced signal for
the PP detecting method increases as the spatial frequency
increases and it becomes maximum at 0.9, and then decreases.
Comparing with the aggregated detecting method, the PP detecting
method has characteristic resemble to the differential detection
without the low frequency element. This indicates that a reproduced
signal with low error ratio can be obtained from the recording
medium 1 by using partial response conformed with this
characteristic.
FIG. 6(a) is a diagram showing a reproduced signal reproduced by
using a DVD (Digital Versatile Disc) player by the PP detecting
method, and FIG. 6(b) is a diagram showing a reproduced signal
reproduced by using a DVD player by the aggregated signal
method.
A DVD player including the reproducing apparatus shown in FIG. 3
reproduces the DVD disc. In FIGS. 6(a) and 6(b) , the horizontal
axis is time, and the vertical axis is an amplitude of the
reproduced signal.
As shown in FIG. 6, the amplitude of reproduced signal using the PP
detecting method is bigger than that of the aggregated detecting
method.
FIG. 7 is a diagram showing a power spectrum of reproduced signal
by the PP detecting method and the aggregated detecting method
reproduced by the DVD player having the reproducing apparatus shown
in FIG. 3. In FIG. 7, the horizontal axis is a frequency (MHz) and
the vertical axis is a power spectrum (dB). As shown in FIG. 7, the
signal ratio in relation to noise for signal reproduced by the PP
detecting method is bigger than that of the aggregated detecting
method. As mentioned above, a reproduced signal in good condition
can be obtained by the PP detecting method.
FIG. 8 is a block diagram showing a decoding circuit 12 for
decoding a tangential push-pull reproduced signal. The decoding
circuit 12 includes a waveform equalizing circuit 13 for equalizing
a tangential push-pull reproduced signal obtained from the light
detector 11 shown in FIG. 3 by compensate the power spectrum in
partial response (hereinafter referred to as "PR") characteristic,
a PLL circuit 14 for outputting a bit clock for sampling a
reproduced signal equalized in the PR characteristic, and a viterbi
decoder 15 for decoding the reproduced signal by synchronizing with
the bit clock and using the output signal from the waveform
equalizing circuit 13. The compensation of the power spectrum is to
obtain a desirable PR characteristic based on spectrum restriction
of the spatial frequency defined by an optical system.
An A/D converter is necessary for converting a signal from analogue
form into digital form before the waveform equalizing circuit 13
and between the viterbi decoder 15. However, it is not shown in
FIG. 8.
The reproduced signal of the pit recording area 2 is decoded as
follows. The tangential push-pull reproduced signal is inputted to
the waveform equalizing circuit 13, and the waveform equalizing
circuit 13 outputs a signal equalized in a desirable PR
characteristic (equalized signal), and the PLL circuit 14 outputs a
bit clock for sampling the equalized signal, and the equalized
signal from the waveform equalizing circuit 13 is inputted to the
viterbi decoder 15 synchronized with the bit clock, and the viterbi
decoder 15 decodes the equalized signal by sampling the signal.
The reproduced signal of the user recording area 3 can also be
decoded in the same way as explained above by using an aggregated
signal.
A decoding method for the pit recording area 2 for a DVD disc by
using a tangential push-pull reproduced signal is explained as
follows. FIG. 9 is a diagram showing a power spectrum of the PR(1,
1, 0, -1, -1) characteristic signal. The horizontal axis is
frequency (Hz) and the vertical axis is power spectrum (dB).
As shown in FIG. 7, the cutoff frequency for spatial frequency
spectrum is approximately 6 MHz. In order to equalize the
reproduced signal into the PR (1, 1, 0, -1, -1) characteristic, the
spectrum of spatial frequency within the range of 6 MHz to 8 MHz is
boosted after the tangential push-pull reproduced signal is
compensated the power spectrum and equalized in desired PR
characteristic by the waveform equalizing circuit 13. The frequency
of bit clock is 26.16 MHz, which is used for DVD clock.
A sampling of the reproduced signal outputted from the waveform
equalizing circuit 13 is taken by the bit clock outputted from the
PLL circuit 14, and an eye-pattern corresponding to five (5) point
of the PR (1, 1, 0, -1, -1) characteristic shown in FIG. 10 is
obtained. FIG. 10 is a diagram showing an eye-pattern by plotting a
sample point of waveform having a power spectrum shown in FIG. 9.
The horizontal axis is time, and the vertical axis is output level
of reproduced signal.
FIG. 11 is a diagram for explaining an intergradation of viterbi
decoder suitable for the PR (1, 1, 0, -1, -1). S0 through S7
indicate the status of viterbi decoder. In FIG. 11, Each S0, S1,
S2, S3, S4, S5, S6, and S7 represents decoded three bits (000),
(001), (011), (111), (000), (100), (110), (111) respectively. The
arrows in FIG. 11 show intergradation from one status to the next
status (for example, S0 to S1) with output in relation to input.
The figure indicated as */* between the status S0 to S7 represents
(input)/(output) bit. In a case of S0 to S1 status, the output bit
is "1" when the input bit is "1".
The sampling of the reproduced signal is decoded by the viterbi
decoder 15 having eight states transition corresponding to the PR
(1, 1, 0, -1, -1). Decoding of the user recording area 3 can also
be carried out by using an aggregated reproduced signal instead of
a tangential push-pull reproduced signal.
As described above, there provided the optical information
recording medium 1 having the pit recording area 2 wherein various
control information are recorded by using a prepit contiguous to
the center of the medium, and having an user recording area 3
wherein a guide groove contiguous to the outer circumference of the
pit recording area 2 and a track in groove format have been formed
therein. There also provided the viterbi decoder 15 for decoding
information from the pit recording area 2 by detecting the
tangential push-pull reproduced signal, and decoding information
from the user recording area 3 by detecting the aggregated signal
so that the decoding of reproduced signal in good condition can be
carried out.
Further, the optical information recording medium 1 includes the
pit recording area 2 having recorded various control information by
a prepit contiguous to the center of the medium, and the user
recording area 3 having a guide groove contiguous to the pit
recording area 2 so that large capacity for recording information
can be increased.
As the reproducing characteristic for a tangential push-pull
reproduced signal in the spectrum of light transmission line is
limited to the given spectrum for bit clock, the tangential
push-pull reproduced signal should be equalized with the PR
polynomial equation in higher order, such as the PR (1, 1, 0, -1,
-1) to equalize in a partial response characteristic. As for a DVD,
the spectrum is limited to 1/4 of the spectrum for bit clock. The
PR (1, 1, 0, -1, -1) can be indicated as 1+D-D.sup.3-D.sup.4,
wherein D is an operator having time delay of one (1) bit.
On the other hand, the aggregated signal is detected by an
equalizing characteristic of a third order PR polynomial equation
such as p+qD+qD.sup.2+pD.sup.3 (p and q are natural numbers) and as
PR (p, q, q, p), and the construction of circuit can be simplified.
Further, the circuit construction can be communized by adopting the
third order PR polynomial equation for tangential push-pull
reproduced signal decoding.
In the next place, there provided an optical information recording
medium wherein an information is recorded in the pit length twice
the standard pit, and the tangential push-pull reproduced signal is
detected and decoded in common with the detection of aggregated
signal.
FIG. 12 is a diagram showing a power spectrum for a signal having
characteristic of the PR (1, 1, 0, -1, -1). The horizontal axis is
frequency (Hz) and the vertical axis is power spectrum (dB). The PR
(1, 1, 0, -1, -1) characteristic is so called EPR4
characteristic.
The EPR4 characteristic can be described as a third order partial
response polynomial equation 1+D-D.sup.2-D.sup.3. As shown in FIG.
12, the EPR4 characteristic requires approximately 1/2 of frequency
spectrum for bit clock. The power spectrum for the EPR4
characteristic is nearly equal to the power spectrum for a PP
reproduced signal shown in FIG. 7 so that its waveform can be
equalized in the EPR4 characteristic by double the length of pit
and bit clock with 1/2 frequency.
The bit clock can be made into 1/2 by dividing the clock frequency
into 1/2 using system controller means not shown with reproduced
area information representing the prepit area.
FIG. 13(a) is a diagram for explaining an intergradation of viterbi
decoder for a PP reproduced signal in the PR (1, 1, 0, -1, -1).
FIG. 13(b) is a diagram for explaining an intergradation of viterbi
decoder for an aggregated reproduced signal in the PR (1, 1, 0, -1,
-1). In FIG. 13, Each S0, S2, S2, S3, S4, and S5 represents decoded
three bits (000), (001), (011), (111), (000), (100), (110), and
(111) respectively in the viterbi decoder. The arrows in FIG. 13
show intergradation from one status to the next status (for
example, S0 to S1) with output in relation to input. The figure
indicated as */* between the status S0 to S7 represents
(input)/(output) bit. In a case of S0 to S1 status, the output bit
is "1" when the input bit is "1".
The viterbi decoder shown in each FIGS. 13(a) and (b) is different
in its targeted value for decoding, and consequently, a common
circuitry can be used for decoding the aggregated reproduced signal
and the PP reproduced signal. After the aggregated reproduced
signal is equalized in the PR (p, q, q, p), the same decoder can be
used for decoding a PP reproduced signal to simplify the decoding
circuitry.
It is obvious that the reproducing operation described above can
apply to, not only to reproduce information recorded in the pit
recording area 2 in twice length of the standard bit length, but
also to reproduce information recorded in multiple of standard bit
length. Further, the circuitry of recording/reproducing apparatus 4
can be simplify as the bit length recorded in the pit recording
area 2 has length n (n; natural number) times of the standard bit
length, and the bit clock is 1/n in frequency, and the state
transition for viterbi decoder 15 applies to the PR
characteristic.
According to an aspect of the present invention, there provided an
optical information recording medium having a pit recording area
with various control information recorded by a prepit, and having
an user recording area with guide groove wherein track has been
formed in groove format therein, and the phase depth of the prepit
and the groove is approximately the same, and the phase depth is
less than or equal to .lamda./10 when the wavelength of reproducing
light source is .lamda., so that a large capacity of information
can be recorded in the user recording area.
According to another aspect of the present invention, there
provided a recording/reproducing apparatus for an optical
information recording medium having a pit recording area with
various control information recorded by a prepit, and having an
user recording area with a guide groove wherein a track is formed
in a groove format therein, including a decoding means for
detecting a tangential push-pull reproduced signal from the pit
recording area, and detecting an aggregated reproduced signal from
the user recording area for decoding operation so that the
reproduced signal can be obtained by a simple circuitry.
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